1. Field of the Invention
The present invention relates to a reclining device which allows a seat back to be rotated about a seat cushion, and, more specially, to one served for a seat of a vehicle, such as an automobile.
2. Description of Relevant Art
Conventionally this kind of a seat recliner has been known with the following constitution. The seat recliner includes: a frame mounted to the base plate of a seat cushion; and a lid mounted to an arm plate of a seat back, the frame and the lid a being rotatable relative to each other. The engagement of a locking gear pivotably mounted on the frame and an internal gear formed in an inner circumferential face of the lid with each other prevents the frame and the lid from their relative rotation. The rotation of a operation shaft through the frame and the lid causes the shifting of the locking gear via a cam plate, the disengagement of the locking gear and the internal gear from each other, and the completion of disengagement to allow relative rotation.
Improvements in vehicle safety are increasingly in demand. The improvement of the locking strength of seat recliner in vehicles is also sought.
The improvement of locking strength, however, is conventionally achieved by means of thickening the base plate or increasing the numbers of engagement teeth. The former results in low formability and high manufacture cost, while the latter is sometimes difficult to adopt due to the limitation of a layout for a large-sized recliner.
The outer circumferential face of the lid is located along the inner circumferential face of the circular recess formed to the frame. The outer circumferential face and the recess have a clearance therebetween, considering product variation.
The clearance causes the engagement of the locking gear and the internal gear of the lid with each other, and the occurrence of a looseness of the seat back without the looseness of the lock mechanism.
It therefore is an object of the present invention to provide a reclining device for a vehicle which has improved locking strength without remaining an increase in the number of engagement teeth or the thickening of a plate.
Another object is to provide a reclining device for a vehicle which minimizes the looseness between the recess of a frame and an outer circumferential face of a lid effectively even if product variation occurs.
To achieve the objects, a first aspect of the invention provides the following reclining device. A frame has a pivot protruding therefrom. The frame is fixed to a first seat component. A first gear is rotatable relative to the frame. The first gear is fixed to a second seat component for establishing an angle between the first seat component and the second seat component. A cam is rotatable to the first gear and with an input component. A second gear is between the pivot and the cam. The second gear is engaged with the cam for rotation. The second gear is to be rotated on the pivot, thus to be locked with the first gear. The pivot has smaller mechanical strength than the first gear and the second gear.
Preferably, the frame has a first guide protruding therefrom. The first guide engages with a periphery of the second gear for guiding the second gear to be rotated on the pivot. The first guide has smaller mechanical strength than the first gear and the second gear.
Preferably, the second gear has a rotational center inside and in proximity to a first tooth of the first gear.
A second aspect of the invention provides the following reclining device. A frame has a pivot protruding therefrom. The frame is fixed to a first seat component. A first gear is rotatable relative to the frame. The first gear being fixed to a second seat component for establishing an angle between the first seat component and the second seat component. A cam is rotatable to the first gear and with an input component. A second gear is between the pivot and the cam. The second gear is engaged with the cam for rotation. The second gear is to be rotated on the pivot, thus to be locked with the first gear. The second gear has a rotation center inside and in proximity to a first tooth of the first gear.
Preferably, the second gear has a second tooth formed close to the pivot.
Preferably, the second gear has a second tooth to be meshed with the first tooth. One of the first tooth and the second tooth has a pressure angle set at a range between 60 and 90 degrees.
Preferably, the second tooth has smaller whole depth in proximity to the rotation center than at another portion.
Preferably, the second tooth has a tip circle with greater radius in proximity to the rotation center than at another portion.
Preferably, the frame includes a first guide protruding therefrom. The first guide engages with a periphery of the second gear for guiding the second gear to be rotated on the pivot.
A third aspect of the invention provides the following reclining device. A frame has a pivot and a second guide each protruding therefrom. The frame is fixed to a first seat component. A first gear is rotatable relative to the frame. The first gear is fixed to a second seat component for establishing an angle between the first seat component and the second seat component. A cam is rotatable to the first gear and with an input component. A second gear is between the pivot and the cam. The second gear is engaged with the cam for rotation. The second gear has a second mating guide engaged with the second guide for guiding the second gear to be rotated on the pivot, thus to be locked with the first gear.
Preferably, the second mating guide includes an opening. The opening includes: a first arced part about the pivot as center; and first plane parts at both ends thereof, the first plane parts having the first arced part therebetween. The second guide includes a projection. The projection includes: a second arced part contacting the first arced part to be slid; and a second plane part to be brought in contact with a first plane part.
Preferably, the second mating guide is embossed as a recess at a central portion of a free end of the second gear.
Preferably, the frame includes a first guide protruding therefrom. The first guide engages with a periphery of the second gear for guiding the second gear to be rotated on the pivot.
A fourth aspect of the invention provides the following reclining device. A frame has a recess with a first circumferential face, and a pivot protruding from the recess. The frame is fixed to a first seat component. A first gear is rotatable relative to the frame. The first gear is fixed to a second seat component for establishing an angle between the first seat component and the second seat component. The first gear is inserted into the recess. The first gear has a second circumferential face facing to the first circumferential face. A cam is rotatable to the first gear and with an input component. A second gear is between the pivot and the cam. The second gear is engaged with the cam for rotation. The second gear is to be rotated about the pivot, to be locked with the first gear. A projection is between the frame and the second gear. The projection is located on one of the first circumferential face and the second circumferential face.
Preferably, the projection projects from the first circumferential face, with a inner diameter of the projection smaller than an outer diameter of the second gear.
Preferably, the projection projects from the second circumferential face, with an outer diameter of the projection greater than an inner diameter of the recess.
Preferably, the frame has smaller mechanical strength than the first gear.
Preferably, the recess has another recess formed at a corner thereof.
Preferably, a reclining device further includes a first lock mechanism for locking between the pivot and the first gear, when a force more than a predetermined value is applied to one of the frame and the first gear.
Preferably, the first locking mechanism further includes a first tooth formed to the first gear; and a first portion formed to the pivot and facing the first tooth. The first portion is deformed to mesh the first tooth.
Preferably, a reclining device further includes: a second lock mechanism for locking between the first guide and the first gear, when a force more than a predetermined value is applied to one of the frame and the first gear.
Preferably, the locking mechanism includes: a first tooth formed to the first gear; and a second portion formed to the first guide and facing the first tooth. The second portion is deformed to mesh the first tooth.
According to the first aspect of the invention, the pivot or the first guide is deformable radially outward. Thus, even if a load is applied to the first gear, the second gear crushes one of the pivot and the first guide. The crushed portion moves radially outward to mesh the first gear, thus preventing the movement of the first gear. This improves locking holding strength considerably.
The pivot is positioned inside and in proximity to the first gear, thus improving in strength. When one of pivot and the first guide is crushed, the crushed portion is facilitated to move radially outward, thus improving in locking strength.
According to the second aspect of the invention, the pivot increases in sectional area, and this improves locking strength and prevents looseness.
The second tooth close to the pivot increases in the number of tooth without the change of layout, thus improving locking strength.
The pressure angle, the whole depth, or the radius of the tip circle allows the smoothing of the engagement and the disengagement of the second gear and the prevention of the lowering of the contact ratio due to the variation of the tooth shapes.
According to the third aspect of the invention, the second gear is supported by the second guide. The second guide prevents the integral rotation of the first gear with the second gear in a locked state, thus enhancing locking strength considerably.
The second mating guide is provided at the central portion the free end of the second gear, thus achieving a reclining device with a high strength and a small size without the change of its conventional structure.
The opening and the projection allow their contact faces to be maximized at a limited range and a receiving face to be enlarged when a load is applied to the second gear, thus enhancing locking strength.
The embossed recess prevents the lowering of the strength of the second gear, thus allowing the prevention from the lowering of the locking strength.
According to the fourth aspect of the invention, the projection allows the effective minimization of the looseness between recess and the second circumferential face of the first gear even if the product variation between the frame and the first gear occurs. This prevents the occurrence of the looseness of a seat back in the locked state of a locking mechanism.
The first or second circumferential face is forced to be inserted into the outer circumferential face of the projection, and this effectively minimizes the looseness between recess and the second circumferential face of the first gear even if the product variation between the frame and the first gear occurs. This prevents the occurrence of the looseness of a seat back in the locked state of a locking mechanism.
The shaving of second gear with the frame causes the assembly of the frame and the second gear with each other, thus preventing the difficult rotation of the second gear relative to the frame.
The coming of the shaved portion into the another recess of frame prevents the axial slight movement of the second gear and the obstruction of the shaved portion to the rotation of second gear relative to the frame.